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Datamation Sort1 Million Record Sort using OpenMP and MPI

Sammie CarterDepartment of Computer ScienceN.C. State UniversityNovember 18, 2004

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Background The Datamation sorting benchmark was

introduced in 1985 by a group of database experts as a test of a processor's I/O subsystem and operating system.

The performance metric is the time to sort 1 million 100-byte records, where the first 10-bytes are the key.

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Sorting Review

The common sorting algorithms can be divided into two classes by the complexity of their algorithms. Algorithmic complexity is a complex subject (imagine that!) that would take too much time to explain here, but suffice it to say that there's a direct correlation between the complexity of an algorithm and its relative efficiency. Algorithmic complexity is generally written in a form known as Big-O notation, where the O represents the complexity of the algorithm and a value n represents the size of the set the algorithm is run against.

The two classes of sorting algorithms are O(n2), which includes the bubble, insertion, selection, and shell sorts; and O(n log n) which includes the heap, merge, and quick sorts.

O(logn) < O(n ) < O(nlogn) < O(n2) < O(n3) < O(2n)

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O(n2) Sorts

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O(n log n) Sorts

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Sorting Example Sorting Example

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OpenMP OpenMP is an industry standard

application programming interface (API) for writing parallel applications for shared memory computers. At the heart of OpenMP are directives, or pragmas, programmers insert to incrementally add parallelism to a program.

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OpenMP – Hello World#include <omp.h> main () { int nthreads, tid; /* Fork a team of threads giving them their own copies of variables */ #pragma omp parallel private(nthreads, tid) { /* Obtain thread number */ tid = omp_get_thread_num(); printf("Hello World from thread = %d\n", tid); /* Only master thread does this */ if (tid == 0) {

nthreads = omp_get_num_threads(); printf("Number of threads = %d\n", nthreads); }

} /* All threads join master thread and disband */ }

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MPI – Message Passing Interface MPI defines a standard library for message passing

that can be used to develop portable message passing programs using either C or Fortran.

The MPI stand defines both the syntax as well as the semantics of a core set of library routines that are very useful in writing message-passing programs.

MPI was developed by a group of researchers from academia and industry, and has enjoyed wide support by almost all the hardware vendors. Vendor implementations of MPI are available on almost all commercial parallel computers.

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MPI – Hello World/* mpicc –o helloworld helloworld.c */

/* bsub –W 2 –I –n 4 mpiexec ./helloworld */

#include "mpi.h"

#include <stdio.h>

int main(int argc,char *argv[]) {

int myrank, numprocs;

MPI_Init(&argc, &argv);

MPI_Comm_rank(MPI_COMM_WORLD,&myrank);

MPI_Comm_size(MPI_COMM_WORLD,&numprocs)

printf("Hello World from process %d of %d\n", myrank, numprocs);

MPI_Finalize();

return 0;

}

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OpenMP and MPI Examples OpenMP Hello World

omp_hello.c (mcrae) OpenMP Sort

ompmerge3.c (mcrae) MPI Hello World

helloworld.c (henry2) MPI Sort

mpimerge5.c (henry2)

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Conclusion Final Sorting Algorithm Description Questions / Comments / Suggestions Contact Information:

Sammie Carterswcarter@ncsu.edu

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References Sorting Algorithms

http://linux.wku.edu/~lamonml/algor/sort/sort.html

Sorting Algorithms Demohttp://www-hm.ma.tum.de/archiv/in2/ss02/vorlesungen/v020606/sort/sort.html

Parallel Programming with OpenMPhttp://www.intel-u-press.com/openmp/summary.htm

Grid Computing (Barry Wilkinson)http://sol.cs.wcu.edu/~abw/CS493F04/slides9.ppt